As this type of plastic foamed article, a plastic foamed article which is a core material used for a headrest for an automobile, configured capable of being attached to a headrest stay, and which protects the rear head part as a buffer material during vibration of the automobile and the like is known, for example (Patent Literature 1).
Such plastic foamed article is provided with a sandwiching portion having a pair of opposite surfaces facing each other. Moreover, the headrest stay has a substantially inverted U-shape and is provided with a pair of rod-shaped insertion portions arranged in parallel and a rod-shaped attaching portion for connecting together one ends of the pair of insertion portions and is configured so that the insertion portions are inserted into a seat body upper part from the other end side thereof.
The plastic foamed article is attached to the headrest stay by pushing the attaching portion into a space between the pair of opposite surfaces so as to sandwich the attaching portion in a radial direction.
Here, in the plastic foamed article, when a distance between the opposite surfaces of the sandwiching portion is larger than a size of the attaching portion in the radial direction, when it is attached to the headrest stay as above, the attaching portion cannot be sandwiched and becomes loose.
Considering the above-described point, the prior-art plastic foamed article is configured so that the distance between the opposite surfaces of the sandwiching portion is smaller than the size of the attaching portion in the radial direction. That is, in a state in which such plastic foamed article sandwiches the attaching portion, the attaching portion is depressed by a predetermined depth on each of the opposite surfaces.